The invention relates to a motion measuring device, particularly for measuring rotation of a body around an axis, said device comprising means such as a coded wheel drivably connected to said body for rotation and having a plurality of holes spaced regularly around said axis and comprising at least one sensor placed on the path of said holes. With such a device, and said coded wheel being mechanically connected to a wheel of a moving object, the distance travelled by said moving object may be determined, as well as the speed and acceleration of said object by measurement of time of displacement.
Known devices of this type typically include a wheel formed by a disk or a cylinder made from a high magnetic permeability material, said measuring wheel having teeth passing in front of the sensor. This solution has the disadvantage of generating a binary electrical signal whose levels are often insufficiently dissociated for allowing measurement under good conditions.